For millions of people with disabilities after stroke, current physical therapy treatment often cannot induce long lasting improvements in arm and hand control. Recent studies show that intensive, repeated practice may be necessary to induce significant treatment effects. However, current service delivery models cannot provide the necessary intensity of practice. One technique that may overcome these limitations is VR. A computerized VR-based system for rehabilitation of hand motor functions has been recently developed. The system creates an interactive, motivating environment where intensity of practice and feedback can be manipulated to create individualized treatment sessions. However, it is presently not clear how this VR training affects finger coordination in real world movements. Moreover, the basics of finger coordination deficits in hemiplegia are poorly understood. The investigators propose a small grant project to obtain preliminary data on the ability of the VR system to induce improvements in the quality of hand motion and finger coordination in functional natural movements. The data collection will be performed before and after four weeks of rehabilitation therapy. Through well-established sophisticated quantitative analyses of finger and hand motion, they will analyze the kinematics of five-finger precision prehension of the hemiparetic arm in chronic post-stroke patients. Subjects will be asked to grasp objects of different sizes, shapes and weights, both stationary and moving. Specific Aim 1 of the study will be to identify deficits in finger kinematics and interjoint coordination prior to training. A main focus will be on the evolution of hand preshaping during movement and its interaction with more proximal degrees of freedom including motion of the trunk. Specific Aim 2 will be to obtain new knowledge of principles of transfer/generalization of VR training to functional real-world movements including grasping. The study will be geared towards obtaining pilot data that will be used to generate an R01 grant application for a more intensive analysis of the topic.